Screening apparatus

ABSTRACT

Screening apparatus includes a main screen deck having a second screen deck attached to the upper surface thereof intermediate its length. The openings in the second screen deck are larger than the openings in the main screen deck for screening out oversize material and allowing the sized material to fall through for normal treatment on the main screen deck. The oversize material is retained on the second screen deck until the vibrations of the second screen deck or a supplemental breaker mechanism breaks or pulverizes the oversize material to a size which allows such material to fall through the second screen deck and main screen deck for recirculation back through a balling apparatus.

United States Patent Sullivan et al.

[ SCREENING APPARATUS [721- Inventors: Paul G. Sullivan; Kenneth H.MacLeod; Joseph E. Kempa, all of Iron Mountain, Mich.

[73] Assignee: The Hanna Mining Company,

Cleveland, Ohio [22] Filed: March 16, 1971 [21] Appl. No.: 124,849

52 us. ..24l/69, 241/81 1 1451 Nov. 28, 1972 1,997,030- 4/1935 Allsweded..24l/69 Primary Examiner-Robert L. Spruill Attomey-Oberlin, Maky,Donnelly & Renner 57 a ABSTRACT Screening apparatus includes a mainscreen deck having a second screen deck attached to the upper surfacethereof intermediate its length. The openings in the second screen deckare larger than the openings in the main screen deck for screening outoversize material and allowing the sized material to fall through fornormal treatment on the main screen deck. The oversize material isretained on the second screen deck until the vibrations of the secondscreen deck or a supplemental breaker mechanism breaks or pulverizes theoversize material to a size which allows such material to fall throughthe second screen deck and main screen deck for recirculation backthrough a balling apparatus.

16 Clains, 4 Drawing figures PATENTED H I 3103,995-

sumtoFz I INVENTORS PAUL 6. SULLIVAN KENNETH H. MACLEOD JOSEPH E. KEMPA@M MQM 6M ATTORNEYS PATENTED I973 3.703.995

SHEEIEDFZ mu T w INVENTORS PAUL 6'. SULLIVAN KENNETH H. MACLEOD JOSEPHE. KEMP/1 BY flhwgm ATTORNEYS SCREENING APPARATUS This invention relatesgenerally as indicated to screening apparatus particularly for use inpelletizing operations for removal of any oversize green balls orgoonies" prior to hardening.

During the pelletizing of iron ore concentrates and other materials, asuitable binder such as bentonite is mixed with the concentrates and thematerial is conveyed to a balling drum or other balling devicewhere itis compacted into green balls. From the balling device the green ballsare directed through an induction or other type heating device to hardenthe balls into pellets. To ensure high quality pellets, it is importantthat the size of the green balls be closely controlled, since if thegreen balls are too large they interrupt the air flow through the bedduring heating and do not heat uniformly, whereas if the balls are toosmall, they fill up the interstices between balls and thus afiect airflow and cause non-uniform heating much in the same manner as theoversize balls.

Undersize balls are readily removed by discharging the green balls fromthe balling device onto a vibrating screen deck which permits theundersize green balls'to fall through the screen onto a conveyortherebeneath for return to the balling device for reprocessing.

Removal of the oversize balls is ordinarily accomplished by providing alarger size screen at the end of the main screen deck or other means andpermits the proper size balls to fall through onto a conveyor fortransfer to the heating device for hardening, but not the oversizeballs. The oversize balls or goonies. are carried along the larger sizescreen for discharge onto a separate conveyor which returns them to thesystem for reprocessing. The disadvantage of removing the oversize ballsin this manner is that it requires additional costly conveyor equipmentto handle the oversize balls.

With the foregoing in mind, it is a principal object of I this inventionto provide a screening apparatus which screens out both the oversize andundersize balls and breaks down the oversize balls or goonies within theframework-of the existing equipment for recirculation back to theballing apparatus for reprocessing.

These and other objects of the present invention may be achieved byproviding in addition to the main screen deck for screening out theundersize material, a second screen deck attached to the upper surfaceof the main screen deck intermediate its length which has largeropenings therein than the openings in the main screen deck for retainingthe oversize material while allowing the proper size material to fallthrough for normal treatment on the main screen deck. The oversizematerial is retained on the second screen deck until broken down orpulverized by the vibrations of the apparatus or by additional breakermechanism to a size which allows such material to fall through thesecond screen deck and main screen deck for recirculation through thesystem for reprocessing.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe an nexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principles of the invention may beemployed.

In the annexed drawings:

FIG. 1 is a schematic fragmentary longitudinal section through apreferred form of screening apparatus constructed in accordance with thepresent invention;

FIG. 2 is an enlarged view of a portion of the main screen deck andpartial screen deck and breaker mechanism of FIG. 1;

FIG. 3 is a fragmentary vertical transverse section through the mainscreen deck and partial screen deck of FIG. 2, taken on the plane of theline 3-3 thereof; and

FIG. 4 is a fragmentary top plan view of the breaker mechanismassociated with the partial screen deck as seen from the plane of theline 4-4 of FIG. 2.

Referring now in detail to the drawings and first especially to FIG. 1,there is shown a preferred form of screening apparatus 1 in accordancewith the present invention for use in pelletizing of iron oreconcentrates and other materials. The screening apparatus 1 generallycomprises a main frame 2 which supports the main screen deck 3 directlybeneath the discharge end of a balling drum or other balling apparatus 5for receipt of the concentrates after having been compacted into greenballs by the balling device. A suitable binder such as bentonite (butnot necessarily limited thereto) is usually mixed with the concentratesprior to enteringthe balling device.

The main screen deck 3 is disposed at a slight inclination as shown andconsists of a plurality of closely spaced rows 6 of rod sections 7 eachhaving downwardly bent ends suitably supported in vibrating supports 8.Between rows there is a clearance space 9 (see FIG. 3) of a size whichpermits the undersize green balls to fall through the main screen deck 3during vibration onto a conveyor 10 located therebeneath forrecirculation through the balling device 5. Preferably, such spacingbetween rows is approximately threeeighth inch for removal of any greenballs of a size less than that.

Retained on the main screen deck 3 between side plates 11 are the largerdiameter green balls, including any oversized green balls, generallyreferred to as goonies, which are undesirable feed for the pelletizingplant since they cause process problems and have an undesirable effecton the quality of the pellets for the reasons previously stated. Toseparate the oversize green balls or goonies from the proper size balls,there is provided a second screen deck 12 attached to the upper surfaceof the main screen deck 3 intermediate the ends thereof and extending ata slight angle therefrom.

As best seen in FIGS. 2 and 3, the ends of the rods 13 which comprisethe second screen deck 12 are desirably supported by rubber holders orother suitable mechanisms 14 and 15 containing holes 16 and 17,respectively, which snugly receive the ends of the rods 13. The rubberholder or other suitable device 14 is confined within a metal supportchannel 18 welded or otherwise secured to the rod sections 7 of the mainscreen deck 3 at the joined end portions 19 which are desirablyvertically staggered as shown. The vertical height of the supportchannel 18 is such that the top flange 20 thereof is substantially flushwith the adjacent ends of the upstream rod sections 7, such supportchannel 18 desirably being fabricated from an angle which forms the back21 and bottom flange 22 of the channel. A separate strip welded to theupper edge of the angle constitutes the top flange 20 which may extendat an angle to provide a narrower opening at the mouth 23 of 1 thechannel preventing pull-out of the rubber holder 14. 1

The other rubber holder or suitable device may be clamped to a supportchannel 24 by a clamp bar 25 using suitable fasteners 26. As shown, thesupport channel 24 has end plates 27 secured to its ends which arefastened to mounting brackets 28 on the side plates 11 for supportingthe downstream ends of the rods 13 which comprise the second screen deck12 vertically above the main screen deck 3.

The spacing 29 between the rods 13 of such second screen deck 12 issomewhat greater than the spacing between the rods 7 of the main screendeck 3. Such spacing 29 may vary within limits to satisfy the specificsize requirements of the product but for this purpose it is desirablyapproximately three-fourth inch. Accordingly, as the larger diametergreen balls are advanced along the incline of the main screen deck 3onto the second screen deck 12 during vibration of the apparatus, thedesired size green balls which are threefourth inch in diameter or lesswill drop through the second screen deck 12 for continued advancementalong the main screen deck 3 and discharge therefrom onto a conveyor 30which transports such desired size green balls to a heating device (notshown) where they are hardened in the usual manner.

The larger diameter green balls or so-called goonie balls are retainedon the second screen deck 12 until the impact of the vibrations of thesecond screen deck or a supplemental breaker mechanism 31 breaks orpulverizes the oversize balls .to a size which allows them to passthrough the second screen deck 12 and main screen deck 3 onto theconveyor 10 therebeneath for recirculation through the system. As shownin FIGS. 1, 2 and 4, such breaker mechanism 31 desirably consists of anelongated pipe 32 loosely supported crosswise on the second screen deck12adjacent the downstream end thereof by a plurality of inverted U-shaperetainer rods 33 secured to the upper edge of the support channel 24.Preferably, three such retainer rods 33 areprovided, equally spacedacross the width of the second screen deck 12, and such retainer rods 33are of a size to permit the pipe 32 to bounce up and down due to thevibrations of the second screen deck 12 while confining the pipe to thedownstream end of the second screen deck. Any oversize material whichreaches the downstream end of the second screen deck 12 is consequentlycrushed between the pipe 32 (commonly referred to as a masher) and therods 13 of the second screen deck 12, the broken particles then passingthrough the second screen deck 12 and main screen deck 3 for return tothe system by the conveyor between said rods is reduced. V 3. Thescreening apparatus of claim I wherein said screen deck as shown toprovide a dam for retaining the oversize balls on the second screen deckuntil sufficiently reduced in size to pass through the second screendeck as aforesaid.

From the foregoing, it will now be apparent that the screening apparatusdisclosed herein provides a unique and efi'ective means for removing andbreaking down the oversize green balls to permit recirculation throughthe system for achieving high quality pellets at reduced cost andincreased efficiency.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Screening apparatus comprising a first screen deck, a second screendeck disposed above said first screen deck in overlying relationshiptherewith, said first screen deck being inclined relative to said secondscreen deck, said secondscreen deck having openings therein of a sizefor retaining the larger size material deposited thereon and permittingthe smaller size material to pass therethrough onto said first screendeck, and a breaker mechanism for reducing the size of the materialretained by said second screen deck for passage therethrough thus toobtain a desired size product with minimum oversize which affects bothquality and production and cost ofproduction, said breaker mechanismcomprising an elongated pipe loosely supported on said second screendeck across the width thereof adjacent the end furthest from said firstscreen deck, and means for vibrating said second screen deck tocause thelarger size material retained on said second screen deck to move towardsaid pipe and said pipe to bounce up and down for crushing the largersize material between said pipe and said second screen deck.

2. The screening apparatus of claim 1 wherein said second screen deckcomprises a plurality of spaced apart rods defining said openingstherebetween, said rods in the region of said pipe being covered bytubing to provide a restricted zone in which the spacing elongated pipeis loosely supported on said second screen deck adjacent the endfurthest from said first screen deck by a plurality of transverselyspaced inverted U-shape retainer rodssecured to said second screen deck,said retainer rods being of a size to permit said pipe to bounce up anddown while confining said pipe therebetween.

4. The screening apparatus of claim 1 further comprising means forpreventing discharge of the oversize material from the end of saidscreen deck furthest from said first screen deck.

5. Screening apparatus comprising a first screen deck onto which thematerial to be screened is discharged, a second screen deck having oneend connected to the upper surface of said first screen deckintermediate the ends of said first screen deck, said first screen deckbeing inclined relative to said second screen deck, means for advancingthe material retained by said first screen deck onto said second screendeck for retention of the larger size material on said second deck andpassage of the smaller size material through said second screen deckback onto said first screen deck, and a breaker mechanism on said secondscreen deck remote from the end connected to said first screen deck forreducing the size of the material retained on said second screen deckfor passage through said second screen deck thus to obtaina desiredsized product with minimum oversize;

6. The screening apparatus of claim 5 wherein said means for advancingthe material retained by said first screen deck comprises a vibratorwhich vibrates said first screen deck.

7. The screening apparatus of claim 5 wherein said breaker mechanismcomprises an elongated pipe loosely supported crosswise on said secondscreen deck remote from the end connected to said first screen deck, andmeans for vibrating said second screen deck to cause said pipe to bounceup and down for crushing the larger size material between said pipe andsaid second screen deck, and means for retaining said-pipe on saidsecond screen deck remote from the end connected to said first screendeck without interfering with such bouncing thereof.

8. The screening apparatus of claim 7 wherein said last-mentioned meanscomprises a plurality of transversely spaced inverted U-shape retainerrods secured to said second screen deck in overlying relation to saidpipe.

9. The screening apparatus of claim 7 further comto provide a restrictedzone in which the spacing between said rods is reduced.

11. The screening apparatus of claim 5 further comprising means forpreventing discharge of the oversize material from the end of saidsecond screen deck furthest from said first screen deck.

12. The screening apparatus of claim 5 wherein said second screen deckcomprises a plurality of parallel spaced apart rods defining saidopenings therebetween, the ends of said rods being supported at one endby said first screen deck.

13. The screening apparatus of claim 12 further comprising a rubberholder for the ends of said rods at one end of said second deck, andasupport channel for said rubber holder, said support channel beingsupported by said first screen deck at the upstream end of said secondscreen deck.

14. The screening apparatus of claim 13 wherein said first screen deckcomprises a plurality of rows of rod sections having verticallystaggered end portions, said support channel being secured to said rodsections at said end portions.

15. The screening apparatus of claim 14 wherein said support channelincludes a top flange which is substantially flush with the adjacent endportions of the upstream rod sections.

16. The screening apparatus of claim 15 wherein the opening to saidsupport channel is narrower than the back wall thereof to resistpull-out of said rubber holder therefrom.

1. Screening apparatus comprising a first screen deck, a second screendeck disposed above said first screen deck in overlying relationshiptherewith, said first screen deck being inclined relative to said secondscreen deck, said second screen deck having openings therein of a sizefor retaining the larger size material deposited thereon and permittingthe smaller size material to pass therethrough onto said first screendeck, and a breaker mechanism for reducing the size of the materialretained by said second screen deck for passage therethrough thus toobtain a desired size product with minimum oversize which affects bothquality and production and cost of production, said breaker mechanismcomprising an elongated pipe loosely supported on said second screendeck across the width thereof adjacent the end furthest from said firstscreen deck, and means for vibrating said second screen deck to causethe larger size material retained on said second screen deck to movetoward said pipe and said pipe to bounce up and down for crushing thelarger size material between said pipe and said second screen deck. 2.The screening apparatus of claim 1 wherein said second screen deckcomprises a plurality of spaced apart rods defining said openingstherebetween, said rods in the region of said pipe being covered bytubing to provide a restricted zone in which the spacing between saidrods is reduced.
 3. The screening apparatus of claim 1 wherein saidelongated pipe is loosely supported on said second screen deck adjacentthe end furthest from said first screen deck by a plurality oftransversely spaced inverted U-shape retainer rods secured to saidsecond screen deck, said retainer rods being of a size to permit saidpipe to bounce up and down while confining said pipe therebetween. 4.The screening apparatus of claim 1 further comprising means forpreventing discharge of the oversize material from the end of saidscreen deck furthest from said first screen deck.
 5. Screening apparatuscomprising a first screen deck onto which the material to be screened isdischarged, a second screen deck having one end connected to the uppersurface of said first screen deck intermediate the ends of said firstscreen deck, said first screen deck being inclined relative to saidsecond screen deck, means for advancing the material retained by saidfirst screen deck onto said second screen deck for retention of thelarger size material on said second deck and passage of the smaller sizematerial through said second screen deck back onto said first screendeck, and a breaker mechanism on said second screen deck remote from theend connected to said first screen deck for reducing the size of thematerial retained on said second screen deck for passage through saidsecond screen deck thus to obtain a desired sized product with minimumoversize.
 6. The screening apparatus of claim 5 wherein said means foradvancing the material retained by said first screen deck comprises avibrator which vibrates said first screen deck.
 7. The screeningapparatus of claim 5 wherein said breaker mechanism comprises anelongated pipe loosely supported crosswise on said second screen deckremote from the end connected to said first screen deck, and means forvibrating said second screen deck to cause said pipe to bounce up anddown for crushing the larger size material between said pipe and saidsecond screen deck, and means for retaining said pipe on said secondscreen deck remote from the end connected to said first screen deckwithout interfering with such bouncing thereof.
 8. The screeningapparatus of claim 7 wherein said last-mentioned means comprises aplurality of transversely spaced inverted U-shape retainer rods securedto said second screen deck in overlying relation to said pipe.
 9. Thescreening apparatus of claim 7 further comprising a rubber covering onsaid elongated pipe.
 10. The screening apparatus of claim 7 wherein saidsecond screen deck comprises a plurality of spaced apArt rods definingsaid openings therebetween, said rods in the region of said pipe beingcovered by tubing to provide a restricted zone in which the spacingbetween said rods is reduced.
 11. The screening apparatus of claim 5further comprising means for preventing discharge of the oversizematerial from the end of said second screen deck furthest from saidfirst screen deck.
 12. The screening apparatus of claim 5 wherein saidsecond screen deck comprises a plurality of parallel spaced apart rodsdefining said openings therebetween, the ends of said rods beingsupported at one end by said first screen deck.
 13. The screeningapparatus of claim 12 further comprising a rubber holder for the ends ofsaid rods at one end of said second deck, and a support channel for saidrubber holder, said support channel being supported by said first screendeck at the upstream end of said second screen deck.
 14. The screeningapparatus of claim 13 wherein said first screen deck comprises aplurality of rows of rod sections having vertically staggered endportions, said support channel being secured to said rod sections atsaid end portions.
 15. The screening apparatus of claim 14 wherein saidsupport channel includes a top flange which is substantially flush withthe adjacent end portions of the upstream rod sections.
 16. Thescreening apparatus of claim 15 wherein the opening to said supportchannel is narrower than the back wall thereof to resist pull-out ofsaid rubber holder therefrom.